Aegis Authenticator - Aegis Authenticator is a free, secure and open source app to manage your 2-step verification tokens...
OTP Auth - The app for calculating one-time-passwords on iPhone and iPad.
Authy - Best rated Two-Factor Authentication smartphone app for consumers, simplest 2fa Rest API for developers and a strong authentication platform for the enterprise.
Authenticator Plus - Authenticator Plus generates 2-step verification codes and lets you synchronize your accounts.
Google Authenticator - Google Authenticator is a multifactor app for mobile devices.
Tofu Authenticator - Tofu Authenticator is an open-source easy to use two-factor authentication app that lets you secure your accounts with one-time passwords.